Audio amplifier



FIG. 1 is a top, front and right side perspective view of an audio amplifier showing my new design;

FIG. 2 is a front elevational view thereof.

FIG. 3 is a rear elevational view thereof.

FIG. 4 is a left side elevational view thereof.

FIG. 5 is a right side elevational view thereof.

FIG. 6 is a top plan view thereof; and

FIG. 7 is a bottom plan view thereof. 

The ornamental design for audio amplifier, as shown and described. 